The present invention relates to stirrup reinforcements for a concrete pipe reinforcing cage. Concrete pipe is typically reinforced by a wire cage comprised of a plurality of circumferential wires joined to a plurality of longitudinal wires extending the length of the cage. Often it is desirable to add additional reinforcement known as stirruping. Stirrups traditionally comprise short lengths of steel wire or rod projecting generally radially from the cage, usually in the areas adjacent to the crown and invert of the cage.
To avoid having to weld a plurality of separate short rods to the cage, prior artisans often employ a generally sinusoidal shaped wire and located in the cage so that it extends longitudinally down the cage with the nose of the sinusoidal member projecting radially from the cage. Heretofore, I have conceived and developed the concept of providing stirrup mat with projections extending therefrom in a plurality of parallel rows. One type of mat which I developed includes circumferentially oriented tie wires which can be manually shaped to conform to the cylindrical configuration of the reinforcing cage at the crown or invert areas thereof so that by manually shaping and locating a single mat (or perhaps two or three for very large pipe or several for 360.degree. stirruping) at the crown or invert area, one completely stirrups that area in a single operation.
I have also conceived and developed a mat in which differentially sized and spaced stirrups are employed. By placing the stirrups closer together in the area immediately adjacent the crown or invert and spacing them farther apart in the more remote areas, and/or by employing taller stirrups in the central area, I concentrate the steel where it is most needed for reinforcement purposes. This invention is disclosed and claimed in my copending patent application Ser. No. 36,170 entitled VAREGATED STIRRUP MAT and filed or even date herewith, now U.S. Pat. No. 4,295,497 issued on Oct. 20, 1981.
Another invention of mine which is particularly desirable where the tops of stirrup projections have to be tied together, as for example in producing arch pipe, is that in which longitudinal lines of stirrup members are hinged to a supporting mat. This enables one to flatten the hinged members and stack mats on top of one another.